deskthority

Surely, this can't be the first one of this type. No, it is obviously not an IBM-made Mac-layout Model M. But it also isn't what one might think it is: a 104-key Unicomp Model M Classic in an IBM case. What I did with this is a little more complicated than that. It's actually a bit of a mutt: it has the barrel plate and control card of a New Model M Mac, but besides the six flippers for the upper nav keys (because I didn't have enough spare IBM ones and this has six more keys than the donor board), the Mac keys, the '+', '=' and 'Clear', the entire rest of the board is a 1988 (I think? maybe 87? I don't have it with me at the moment) 1391401.

I have three 1391401s, two of which I have owned for something like 30 years, both 1988s, and this one, which I had originally bought as a keycap donor for a New Model M. This one has been the 'best' of them and I had put away to 'preserve' it, since when I first got it, almost all of its tendons had been intact. But when I opened it up a few weeks ago trying to decide which 1391401 to screw mod first, 60% of them had fallen off in the interim! It was now, by far, the worst.

So I took it to my workbench in the basement, and set about removing what was left of its tendons after drilling a pair of holes in the middle right and left tendons (the way I do it is first drill those two and install a 2.5mm nut and bolt, then I cut off that row, drill them with a smaller bit, cut off the rows above and below them, and drill those, and work my way to the edges thus. That way the angle of the mounting plate is correct to the curve while they are drilled; I find the most success with this) and installing the usual bolt/screws.

But when I finished this and removed the bolt, the thing flopped like a newspaper. The barrel plate had numerous serious cracks. Building a conversion like this had been on my mind; in fact I had started a conversation with Unicomp to order a 104 barrel plate, membrane, USB cord, and control card for a Mac. But the fact is, I have two New Model M mac boards, and while I want to keep one to use as a reference of what new Unicomps are like, I don't even enjoy using them. I'll probably still buy the parts for reasons I'll explain, but I figured, why not?

So I drilled out the New Model M, and swapped its membrane and barrel plate on to the mounting plate, springs, and mat of the 1391401, deciding on a whim to also convert it to an ISO layout. Dunno if that will work out. I had the idea that this type of board might be marketable in limited quantities, because without talking smack about Unicomp's products (which are an impressive value, frankly) there is no substitute for a real IBM M.

In some ways this was a great success. I had not liked the 'feel' of the NMM; its too sharp, especially in sound... almost like a pastiche of a Model M. I had thought they were great when I first got them, which is how I ended up with two, but then I made the mistake of breaking out one of my IBMs and... yeah. That led me down a many thousand dollar rabbit hole into M122 Type I hoarding, bolt modding, a Model F122s, oddball M collecting, and ordering a B122 from Joe. The goal was a intuitively Mac compatible board with all of the feel of a second gen IBM Model M. In terms of all of the feel stuff, I accomplished that.

Just one little problem; it doesn't work. AFAICT, all the lock lights light up and stay on, but it is otherwise nonresponsive. I suspect the problem is that I screwed up wiring the new Unicomp control card to its membrane, but I was too tired to dig into it. The way the new membrane wires in and works is a little unclear to me, because it seems like there is just one 'edge connector' (its not really an edge connector), which makes no sense. I hope I don't need to unscrew it, but... in any case, I need to take it apart with and need my T7 torx driver. Depending on the weather, I may do it tomorrow (if the weather is good, I have a noise-reduction project I want to get done on my van before it gets too hot...)

Anyway, I think I can market conversions like this, in limited quantities. I'd need a source of lowerish cost IBM Model Ms, ideally ones that are not cosmetically 100% perfect, have broken tendons, and ideally a cracked barrel plate or bad control card. I'd prefer not to do this (not reversible) modification to a really good example board.

Update, thing works perfectly now. The new control card does work with one connector, I don't know how, but the problem was that the simply-touch-ribbon-cable-to-the-right-place-on-the-card-and-screw-them-together is a bit of a faff. Once I got it lined up properly, it works just fine. Incidentally, production date for the 1391401 is 10/26/87.